In recent years, more and more use is being made of stools in dental operatories, as well as in other types of operatories, where it is desired to have an arm, frequently of a curved nature, pivotally mounted for adjustable positioning within a horizontal plane parallel to the seat with which the arm is associated. The user of such stools, such as either a dental assistant or a dentist, or other medical personnel, sometimes uses such arms as a backrest or an armrest and, in certain circumstances, as a rest against which the abdomen or chest of the operator is disposed for suitable support incident to conducting certain medical operations, dental or otherwise. The present invention particularly is concerned with pivotal support of an arm, including a curved arm, associated with a stool or other form of seat so that the position of the arm may be adjusted, as desired by the person sitting upon the seat, and thereby dispose the arm as best suited for certain operations by the person on the seat. The invention is particularly concerned with clutch means to control such positioning of the arm.
The pivoting of support arms relative to seats is a matter that has been dealt with in a number of prior circumstances. By way of example, one prior U.S. Pat. No. 1,706,634, to Seils, dated Mar. 26, 1929, concerns an armrest adjustably supported relative to the door of an automobile adjacent the seat for the driver. Various positions are possible by means of a ball and socket arrangement, as well as a vertical pivot.
In dental stools in which patients are supported, it also has been desirable to provide one or more of the arms at opposite sides of the seat of the dental chair with means to pivot the arm either sidewise or upward to facilitate the seating or removal of a patient with respect to the chair and various positioning means have been devised, as illustrated, for example, in prior U.S. Pat. Nos. 3,829,159 to Leffler, dated Aug. 13, 1974 and 3,950,027 to Wilson, dated Apr. 13, 1976.
Still another prior U.S. Pat. No. 4,085,967 to Spencer, dated Apr. 25, 1978, and assigned to the same assignee as the instant invention, pertains to a dental operatory stool in which a curved arm is adjustable with respect to a seat for purposes of moving the arm laterally, as distinguished from about a vertical pivot relative to the seat, the arm of said stool being similar to the arm of the present invention, as far as shape is concerned, and also is supported at the upper end of a plurality of arms having portions extending vertically above the level of the seat of the chair or stool.
Another relatively simple structure for pivotally supporting arms on the frame of a seat or chair for movement in vertical planes comprises the subject matter of prior U.S. Pat. No. 4,118,069 to Hunter, dated Oct. 3, 1978.
While the foregoing patents illustrate certain pivotal means and position-retaining mechanism for arms movable relative to seats of various kinds, they fail to provide an arm of the type comprising the present invention for the purpose described below with respect to said invention.